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Geometric Attributes: Program apparent_cmpt

Attribute-Assisted Seismic Processing and Interpretation 31 May 2021 Page 1

COMPUTING APPARENT DIP AND AMPLITUDE GRADIENTS – PROGRAM apparent_cmpt

Contents

Apparent curvature computation flow charts ................................................................................ 1

Computing apparent components .................................................................................................. 2

References ...................................................................................................................................... 9

Apparent curvature computation flow charts

inline dip crossline dip

apparent_cmpt

p(φ=-900)

p(φ=-600)

p(φ=-300)

p(φ=00) p(φ=+30

0)

p(φ=+600)

p(φ=+900)



Computing apparent components

Most modern workstations provide a “calculator” function that circumvents the need to use program apparent dip. If this is the case, the apparent dip at φ=300 is computed using the formula p(φ=300)=p cos(300)+q sin(300). where p is the inline dip component and q is the crossline dip component computed using program dip3d. Program apparent_cmpt will compensate for rotated and counterclockwise survey axes. To invoke program apparent_cmpt, click the Volumetric Attributes tab and select apparent_cmpt (See image on following page) :

inline grad crossline grad

apparent_cmpt

g(φ=-900)

g(φ=-600)

g(φ=-300)

g(φ=00)

g(φ=+300)

g(φ=+600)

g(φ=+900)



The following GUI appears:

The parameters are fairly obvious. Enter the inline dip and crossline dip component file names at bottom of the panel. In this example, I have entered values of 0 for the first azimuth, 150 for the last azimuth, and 30 for the azimuth increment, which will result in apparent dip components at 00, 300, 600, 900, 1200, and 1500. Note that components at 1800, 2100, 2400, 2700, 3000 and 3300 would be identical but with opposite sign. Program apparent_cmpt is not computationally intensive; within a few moments the following output files are generated:

Note how the azimuth values of 0, 30, 60, 90, 120, and 150 have been added to the end of the file name. If the inline axis is oriented North and the crossline axis East, apparent_cmpt will reproduce the inline and crossline components of dip at 00 and 900. For the GSB survey, the



inline axis is at +250 and the crossline axis is at -650 (counter-clockwise survey axes). These latter two input files look like the images below:

Plotting the results of apparent_cmpt at the same time slice, we observe the inline and crossline dip components correctly plotted at 00 and 900, along with the other components.



To compute apparent amplitude gradients, simply click the Apparent Amplitude Gradient tab and enter the inline and crossline energy gradients:



The amplitude gradients for the Great South Basin GSB_small survey look like the following images on the next page:



Mai et al. (2008) developed this algorithm to analyze the fractured Cuu Long Basin, Vietnam. As before, we plot the inline gradient (at 1600) and crossline gradient (at 700) through the basement high at t=2.8 s as reference images:

The results of apparent_cmpt look the following images on the next page.



References Mai, H.T., K. J. Marfurt, and T. T. Mai, 2009, Multi-attributes display and rose diagrams for

interpretation of seismic fracture lineaments, example from Cuu Long basin, Vietnam: The 9th SEGJ International Symposium Imaging and Interpretation - Science and Technology for Sustainable Development, paper 1D93.

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Geometric Attributes: Program apparent cmpt COMPUTING ...mcee.ou.edu/aaspi/documentation/Geometric_Attributes-apparent_c… · program apparent dip. If this is the case, the apparent